I recently wanted to install gentoo on my Ultra5. Booting etc. worked fine, but I wasn't able to get my net working.
NIC was detected correctly (SUN Happy Metal), it got the ip-address from dhcp, too. But now everything is going _very_ strange: I'm not able to ping anything. A tcpdump on my local server shows all icmp echo-requests from the Ultra to my workstation, the workstation replied as expected ... but the Ultra only shows "destination unreachable". I looked after the arp-tables on both machines and, surprise, both got the correct entries for each other!
Same procedure with my server ... with same result => "destination unreachable", arp-entires correct. Same result the other way round, too.
I tried again with manual ip-settings, but without success :/

I read the thread you pointed me to before, but it's not the situation I got here. I'm not able to ping anything, not even my gateway. My firewall is not blocking any internal traffic, too. But yes, I double-checked anything (IP, netmast, broadcast, gateway, correct routing-table, firewall etc.pp.).
And I tried ssh, too ... with the same result: no connection, only arp-requests.

Next thing I'll try tonight is setting arp-entries by hand ... but maybe someone has a better solution?

Bye,
Michael_________________Although the Perl Slogan is There's More Than One Way to Do It, I hesitate to make 10 ways to do something. :-)
--Larry Wall in <9695@jpl-devvax.JPL.NASA.GOV>

Depending on who is administering your network, pings may be
useless. On my campus, CMP traffic is limited on the Cisco switch
level, so it has nothing to do with what firewalls are in use.
I can't ping between 2 machines that I control even when
there is no firewall operating.

Well, it's my own network at home, so I know what's restricted/allowed in there ;)
Nevertheless, as I said before, I tried ssh with the same result => no connection.
I tried telnet with some external IP's, too (eg. my server at our company or 216.239.59.99:80).

Setting arp-entries by hand did not solve the problem, so I have to think about sth. other ...

Bye,
Michael_________________Although the Perl Slogan is There's More Than One Way to Do It, I hesitate to make 10 ways to do something. :-)
--Larry Wall in <9695@jpl-devvax.JPL.NASA.GOV>

Depending on how well you know networking (it sounds like
you know it quite well) you might want to try using
route commands rather than manipulating arp tables directly.
Sometimes the lower level approach provides too much
room to make a mistake.